Hazard Analyses, in Reference to Bacillus cereus, of Boiled and Fried Rice in Cantonese-Style Restaurants1

Abstract

Hazard analyses were conducted in six Cantonese-style restaurants to evaluate the amount of Bacillus cereus in rice and the water activity and the temperatures of rice at each stage of processing. Each of 16 samples of raw, polished rice contained B. cereus. The water activity of cooked rice ranged from 0.912 to 0.980, and was related to the stage of the processing and storage practice. Rice reached temperatures that exceeded 93 C (200 F) during cooking. Cooked rice held in steam tables was maintained at temperatures that should preclude growth of B. cereus. Whenever cooked rice was kept at room temperature for a few hours, the temperatures became such that considerable growth of B. cereus could have occurred. Rice in layers less than 9 cm (3.5 in.) thick cooled rather rapidly; layers thicker than 9 cm (3.5 in.) cooled more slowly. During frying and refrying, temperatures exceeded 74 C (165 F). B. cereus was frequently isolated from rice at various stages of preparation and storage, but in numbers fewer than 103 per g. This organism was also isolated from rice storage pans. Recommendations for preventing problems that could be caused by B. cereus as a result of preparation and storage practices are to (a) cook only small batches of rice at intervals during the day, (b) hold cooked rice at or above 55 C (131 F), (c) cool cooked rice in shallow pans in layers less than 9-cm (3.5 in.) thick and (d) fry rice so that every grain is certain to reach a temperature of at least 74 C (165 F).